Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Centra-drive upgrade

I'm not sure where you would get a torque wrench that would read that high.

This is from our CVO Harley forum from over 10 years ago. This particular Harley motor uses the same crank configuration that S&S does, or I should say that S&S uses the same configuration as Harley... In '06 Harley went to a full-length finer spline primary side crank end with a center bolt. But prior to that, Harley used that same crank spline and threaded crank end back into the early 60's at least on the Panheads, Shovelheads and EVO's. Carrying that same up to '06 with the new Twin Cam motors.

This is the same nut that Harley uses for their compensator retention.

Put a couple drops of oil under the head of the nut, where the nut pushes against the outside shell of the compensator. Put two drops of #262 red Loctite on the threads of the crankshaft, install the compensator assembly and nut, torque the nut to 150 - 165 ft/lbs.

I know back in the 60's with our VW dune buggies, the crank/flywheel nut was torqued to 200 ft/lb and it took several of us to hold the motor and then lay on the pipe over the torque wrench.

I haven't looked at my setup for some time now, with the move and all, but I'm guessing maybe 3/4" threads, maybe a bit less on the crank. The cranks are not heat treated, per se, but I would guess somewhere between a grade 2 to grade 5 in hardness. Definitely NOT grade 8. A 3/4" US Fine thread is maxed on grade 5 at 235 ft/lb. Grade 8 max is only 315 ft/lb. I can't believe the end of the crank doesn't break off, just my opinion only and I've NOT done any of the testing that Phil had gone through. This is ONLY my personal thoughts, and I cannot back any of it up...

Dan... I had the same thought, I just cannot wrap my head around 450 ft/lbs. Maybe someone did the metric to standard conversion backwards

The S&S "T" Series engines, which are large displacement engines, have the following torque spec listed for their "compnsator nut".



These engines can get larger than the 121" X-Wedge. 111" , 124" , 143".

But these presumably don't use a Centa compensator.

The original question was about the recommended torque for the Phil Bleazey conversion and, as Rog said, Phil uses the specified torque for a 7/8 UNF nut which is 440 ft/lbs.

The MMC engine build up manual used when replacing the HD drive with a Centa unit states 170 ft/lbs.
That's on a 'half nut' which is actually a 2/3rd nut if comparing length.
That's with a flat washer/star washer and no Loctite.

I wonder where he got that torque figure? I just looked at several charts for graded fasteners, and for bare (unplated and un lubricated) the torque for Grade 5 is about 475lbs/ft. For plated and lubricated bolts the torque is more like 350. For Grade 2 it's about half that, and for grade 8 about 40% more. Bolts all have rolled thread which are generally stronger than the machined threads as found on the crankshaft. So to come up with a suitable torque for a 7/8" machined thread in an unspecified steel would be a non S swag, IMO. Perhaps Phil was able to determine the type and hardness of the crankshaft and extrapolated from there?

The thickness of the nut may or may not have an impact on the torque figure. I was taught you need at least 1 diameter (of the male thread) of thread engagement to achieve full strength in a bolted joint, with 1.5 diameters preferred in order to provide a margin of safety. So if the 'thin' nut is roughly 7/8" tall then there is little to be gained by a deeper nut.

One assumes this utilises at least a fresh unused star washer and perhaps a new flat washer and/or nut...all of which in theory would seem to produce a new "positive lock".

Is 440 ft/lbs with no star washer in the particular environment better/worse?

I would say 440 ft/lbs seems excessive but with no star washer it may need to be tighter perhaps, I would worry about the effects of tightening to this on the shaft, nut and thread when the original torque is 170 ft/lbs and be inclined to refit as factory torque and setup (with star washer) to be safe

One issue is that originally Phil instructed all to discard the flat washer and only use the star washer and new full nut.
And to tighten to 'around' 400 lbs/ft.

The reason for discarding the flat washer was so that a full nut could be used as otherwise there is not enough thread on the crankshaft end to make it worthwhile fitting the full nut.

Then the issues started with the nut coming undone and it was discussed at the time that it could be due to the flat washer being discarded. Phil stated it wasn't due to this and entirely due to crank/hub fitment....

I instead reverted my upgrades back to original setup of flat/star/half nut as personally I didn't believe that the missing flat washer wasn't something to do with the failures that were starting to occur, in conjunction with the roller issue.

And now, thanks to this forum, I have learned that Phil is now using the flat washer, discarded the Star washer and using Loctite....

When my mate and I did the upgrade in Phill's I too questioned him on the flat washer I cant say I was too happy about it but bowed to his superior Knowledge of the wee beastie. A word of caution however after nearly full assembly when we turned over the mechanicals there was a grinding noise and after a further strip down we found one of the magnets had detached itself. He re glued it and we re assembled. Phill and my mate went for a test in the upgraded three wheeler and I followed in Phill's it drove like a bag of spanners. When we got back I said it wollowed a bit in the corners and asked him to show us where they had been cracking, If my memory is correct he had already butt welded his own chassis but we found another crack that morning.Your cars are showstoppers guys but you need a sense of humour and a lot of patience to look after them.....